How to delete PREFIX_NEW(team ID).com.mydom.myapp or TestFlight builds using it?

So, first terminology:

• Your Team ID is a 10 character code that identifies your team. For example, SKMME9E2Y8 is my individual Team ID.
• A bundle ID uniquely identifies your app, typically using reverse DNS notation. For example, com.example.test798928.
• An App ID is a bundle ID combined with an App ID prefix. For example, SKMME9E2Y8.com.example.test798928.
• An App ID prefix is either your Team ID or a unique App ID prefix.
• A unique App ID prefix is a 10 character code that’s allocated to your team, different from your Team ID. For example, one of my teams is allocated the App ID prefix of VYRRC68ZE6. App ID prefixes are effectively deprecated.

If you previously used a unique App ID prefix for your app, you should be able to continue to use that same App ID prefix. Where is no requirement to migrate to using your Team ID [1].

Which brings us to this:

But I cannot update it anymore because its AppID that appears in my account … is PREFIX_NEW(team ID).com.dom.myapp, incorrectly prefixed by the now recommended default prefix (Team ID).

I’m not 100% sure what’s going on here, but it sounds like something migrated this App ID from its unique App ID prefix to your Team ID. That’s something you can explicitly request, but it shouldn’t happen spontaneously.

You have two choices here:

• You can publish the app with the new prefix. That’s a good idea in general, but it does have some specific drawbacks. Specifically, you have to be careful if your app uses the keychain. See App ID Prefix Change and Keychain Access.
• You can ask Apple to migrate the app back to the original unique App ID prefix. If you want to do that, you’ll need to contact the Developer website folks officially via Apple > Developer > Contact Us.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

[1] Although there are good reasons to do so, including:

• If you want to publish a macOS version of your app.
• If you want to share data, like keychain items, between this apps and other apps from your team.

Thank you Quinn for the quick answer. It is also very thoughtful to give the definitions of the terms, really helpful to me. Reading your post and the referenced one, my app does not manage keychain items such as user's passwd, so the loss of keychain items is not an issue for me, I conclude the best approach for me is to follow your recommendation "publish the app with the new prefix. That’s a good idea in general".

If I publish the update (new version) of my app with newer App ID Prefix while keeping the same bundle ID, will my current customers be able to install the update fo free as the same app that they already payed for? In other words, will iPhone considers that they are the same app despite the difference in APP ID Prefix (but always with same bundle ID) ?

will iPhone considers that they are the same app despite the difference in APP ID Prefix (but always with same bundle ID)?

Yes.

Our platforms use the bundle ID to track an app’s identity. The App ID is primarily there to tie the app to its provisioning profile, which is important but not the key to the app’s identity.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"